In recent years, a variety of fields such as optics, magnetic recording, precision machining, and printing demand a displacement element for controlling, for example, the length or position of an optical path in the order of a submicron or vibrations precisely. As such a displacement element meeting the above demand, there is one employing displacement provided by a reverse piezoelectric effect or an electrostrictive effect taken place when the voltage is applied to a piezoelectric/electrostrictive material made of, for example, a ferroelectric substance.
Conventionally, as such a displacement element, a laminated piezoelectric element 100, as shown in FIG. 34, which is disclosed in Japanese Patent First Publication No. 4-309274 is known. The piezoelectric/electrostrictive element 100 includes, as shown in FIG. 34, a lamination 104 formed by laminating a plurality of piezoelectric ceramic layers 101 and electrode layers 102 alternately and a pair of electrically insulated external electrodes 104 and 105 which connect the electrode layers 102 alternately on opposed side surfaces of the laminate 103 and are so formed as to extend to upper and lower surfaces of the laminate 103. In the laminated piezoelectric element 100, ridges defined by the side surfaces and the upper and lower surfaces of the laminate 103 are rounded to an extent where the radius of curvature of the ridges exceeds half the thickness of the piezoelectric ceramic layers 101.
The production of the laminated piezoelectric element 100 shown in FIG. 34 is accomplished by first weighing and grinding raw material, mixing it with binder, and defoaming the mixture, after which the mixture is shaped into a sheet from which rectangular green sheets 101 A are punched (which will be the piezoelectric ceramic layers 101 by baking). A conductive paste is printed over a given area of one surface of the green sheet 101A to form the electrode layer 102. Next, the green sheets 101A on which the electrode layers 102 are printed properly are, as shown in FIG. 35, laminated and bonded by pressure and cut as needed after which it is baked to produce the laminate 103 as shown in FIG. 36. As a result, the green sheets 101A are, as mentioned above, baked to produce the piezoelectric ceramic layers 101. In the laminate 103, arrangement positions of the electrode layers 102 are predetermined on a pair of opposed side surfaces thereof so that the electrode layers 102 may be exposed alternately. Afterwards, on given areas of upper and lower surfaces of the thus produced laminate 103, an external upper surface electrode 104A, and an external lower surface electrode 105A are formed. Next, on a pair of opposed side surfaces 106 and 107 to which the electrode layers 102 of the laminate 103 are exposed alternately, external side surface electrodes (thick film electrodes) 104B and 105B are formed to make the laminated piezoelectric element 100 shown in FIG. 34. The external side surface electrode 104B is so formed as to connect with the external upper surface electrode 104A, while the external side surface electrode 105B is so formed as to connect with the external lower surface electrode 105A. As a method of forming the above-mentioned external electrodes 104 and 105, there is a dipping method or an evaporation method.
FIG. 37 shows an actuator 200 utilizing the thus constructed laminated piezoelectric element 100. The actuator 200 has the laminated piezoelectric element 100 secured on a movable plate (diaphragm) 110 by an adhesive 111.
As another displacement element, a piezoelectric displacement element, as disclosed in Japanese Patent First Publication No. 63-295269, is known which is equipped with a plurality of opposed inner electrode layers in a ceramic thin plate exhibiting the piezoelectric effect. Corners that are boundaries of side surfaces and upper and lower surfaces of the ceramic thin plate are chamfered mechanically. On front and reverse surfaces and the opposed side surfaces of the ceramic thin plate, a pair of opposed surface electrodes connecting with internal electrode layers is so formed that the electrodes are electrically insulated from each other. The opposed surface electrodes are formed on the surfaces of the ceramic thin plate by a physical vapor deposition method such as a sputtering method or a vapor deposition method or a film forming method such as plating.